This invention relates to apparatus for obtaining data from a test specimen to determine Poisson's ratio for the test specimen.
Extensometers have been used for measuring the decrease in width when a sample is elongated in a tensile test machine. These cannot be used where attachment to the sample results in damage to the sample which can result in premature rupture of the sample and in other ways affect the test results.
In testing soft materials such as solid rocket propellant gas dilatometers have been used wherein changes in the total volume of the material is determined by a change in pressure within a chamber. These systems are costly and difficult to use and the system is highly sensitive to temperature change. Liquid dilatometers are less temperature sensitive but it must have the liquid circulated for temperature control and is not easy to use. Also these cannot be used where the liquid will have an adverse effect on the test sample.